Process for the production of metallic calcium.



No. 808,066. PATENTED DEC. 26, 1905. W. BORCHERS & L. STOGKEM.

PROCESS FOR THE PRODUCTION OF METALLIC CALCIUM.

APPLICATION FILED OCT. 24,1902.

Witnesses-- MW Attorney.

UNITED STATES PATENT OFFICE.

l/VILHELM BORCHERS AND LORENZ STOCKEM, OF AACHEN, GERMANY.

PROCESS FOR THE PRODUCTION OF METALLIC CALCIUM- Specification of Letters Patent.

Patented Dec. 26, 1905.

I Application filed October 24,1902. Serial No. 128,637-

To all whom it rmty concern.-

Be it known that we, WVILHELM BORCHERS, of 15 Ludwigsallee, and LORENZ STOCKEM, electrochemical engineer, of 64: Pontstrasse, Aachen, Germany, subjects of the German Emperor, have invented a new and useful Process for the Production of Metallic Calcium, of which the following is a specification.

According to the publications on calcium and its production known up to the present day the process of electrochemically producing this metal from its fused compounds in quantities exceeding a few grains had to be considered as one of the most diflieult problems of electrometallurgy. (Compare Boreherss Elect;'omemllurgy, second edition, pages 72/82.) Even the latest researches of Professor Moissan, Paris,( Oomptes Remlus, 1898, Vol. 126, page 1753,) on the electrolysis of calcium iodid have only established the fact that metallic calcium will disengage from molten iodid of calcium in the form of small crystals and globules, which may be found after cooling scattered through the salt mass. N ow we have found that metallic calcium can not only be deposited but easily recovered from electrically-molten chlorid of calcium or other suitable calcium haloid salt in any desirable quantity by keeping the temperature of the electrolyte at least at and around the cathode at a moderate red heat not exceeding the melting-point of calcium metal, employing at the same time an electric smelting apparatus, which will allow the use of a comparatively small cathode against a largeanode. Under these precautions calcium will be deposited in the shape of a soft sponge upon the cathode. This metallic sponge is coherent enough to allow to be fished out by means of a spoon, a blade, or other suitable instrument. Taken out in this manner and immediately dumped into kerosene-oil or other suitable liquid to prevent oxidation of the spongy metal by the oxygen or the moisture of the air a crude metal is obtained containing from fifty to sixty per cent. of pure calcium, the rest being adhering calcium salts. If, however, the deposited sponge before lifting it out of the electrolyzing vessel is caught by a pair of tongs the jaws of which should have been heated before use, and if the sponge is now pressed between the jaws of the tongs the larger part of the calcium salt inclosed in the pores of the sponge will squeeze out, while the heretofore spongy mass will now weld together into a solid plate, which may now be taken out of the electrolyte and cooled without serious danger in the open air. Such plates cut by a knife or chisel will show a bright white metallic shine upon the cut surfaces. This pressed metal contains up to ninety per cent. pure metallic calcium still inclosing calcium salt from the electrolyte in the pores.

It will be understood that instead of tongs other instruments than those named may be employed for taking out the metallic sponge as well as for compressing it.- This would of course not make any alteration in the process according to which the calcium is compressed before being taken out. The metal thus produced may be employed for many purposes in its present condition; but it may be melted down into pureealcium in air-tight receptacles, so as to remove the salt still contained in it.

Instead of calcium chlorid other calcium salts may be employed, especially calcium fluoridfluor-sparwhile an addition of fluor-spar to calcium chlorid does not unfavorably influence the result. It is, however, preferred to employ calcium chlorid, inasmuch as it is one of the cheapest calcium salts and asits melting-point is high enough that when exceeded within moderate limits the temperature most favorable for the formation of the sponge may be attained without much measuring. Any increase of temperature over the melting-point of the calcium metal during electrolysis causes unnecessary loss of heat and favors thesolution of the calcium metal.

For carrying the process out experimentally a simple electric furnace was employed, the wall of which consisted of a cylinder of carbon connected to the positive pole of a source of current. The cylinder was closed atits lower end by a cooling-body and insulated from the latter by suitable means. An iron rod was employed as cathode, which was fixed on the cooling-body and projected upwardly into the furnace. The bottom of the furnace was for the purpose of providing a tight closure covered with a layer of fluor-spar, which on account of its higher melting-point and inconsequence of the cooling from below did not liquefy.

To start working, the furnace just de scribed is charged with a quantity of calcium chlorid, the fusion of which may be effected by introducing between the carbon cylinder and the iron rod or cathode a number of heating resistances consisting of thin carbon rods 'lIC which after the fusion of the electrolyte is effected are taken out, whereupon the electrolysis at once commences.

The chlorin separated at the anode may be conducted OE and utilized in a known manner, While the calcium metal settling on the cathode may be taken out in the manner hereinbefore described.

For carrying out the process we have employed an experimental apparatus, illustrated in the drawings.

Figure l is a vertical cross-section thereof, and Fig. 2 is a View from above. Fig. 3 shows part of the metal sponge taken out by a pair of tongs.

Equal letters refer to equal parts of the apparatus.

The apparatus so far employed was a small electric furnace, the side wall of which consisted of a cylinder at, of carbon, put together by carbon staves like those of a barrel. The cylinder was closed at its lower end by a cooling-body Z) and insulated from the latter by a hollow cylinder 4 of electrically non-conducting but fireproof substance, such as fire-clay. An iron rod 0 was employed as cathode, which was fixed on the cooling-body b and projected upward into the furnace. The bottom of the furnace was for the purpose of providing a tight closure covered with a layer of fluorspar f, which on account of its higher melting-point and in consequence of the cooling effect of the body I), through which cold water was kept running, did not liquefy entirely. To start running this furnace, it was charged on top of the fiuor-spar layer f with a layer of calcium chlorid e, the fusion of which may be effected by introducing between the carbon cylinder at and the iron rod 0 a number of heating resistances, consisting of carbon rods 1, in which the electric current passing the circuit a r r r c is converted into heat, smelting the calcium chlorid surrounding the rods 1". As soon as now the rods 7 are taken out electrolysis commences between the anode a and the cathode 0, calcium metal depositing at the cathode and chlorin at the anode. In our experimental apparatus the chlorin was allowed to escape. There should be only enough current supplied to the apparatus to keep the chlorid of calciumin a molten state. The quantity of current of course will vary with the size of the apparatus. The cathode should be kept cool enough by water circulating through the cooling-body b that the calcium metal depositing upon the cathode will be prevented from melting. Molten calcium metal will readily dissolve in calcium chlorid, (CaGh) and combine with the latter to calcium subchlorid, (Oa2Cl2.) This was the reason why calcium metal could not be made in large quantities by the methods heretofore known. All of these methods aimed to obtain molten calcium metal, which dissolved to the largest part to form subchlorid, as just stated, and this salt was transformed back to calcium chlorid at the anode, where free chlorin is always present during electrolysis.

If the cathode was kept cool enough, the

calcium metal will form a spongy mass, (shown at 8, Figs. 1 and 3,) and now it will no longer dissolve; but if dipped out inthis loose spongy state, the calcium will quickly oxidize in the open air. Therefore to prevent oxidation and for the purpose of squeezing as much calcium chlorid as possible in order to obtain a concentrated metal the sponge while in the furnace is caught by a pair of flat checked tongs and pressed, and only after pressing is lifted out of the electrolyte, as shown in Fig. 3. Fig. 3 shows part of the metal taken out, part of it to be caught next left at the cathode. It will be seen from this description that the apparatus may be easily changed in a large variety of manners and yet serve the same purpose and comply with the conditions of our process.

We do not claim the invention of an apparatus for making/calcium metal; but

What we claim as new against the method of electrolytic recovering metals known up to date is- 1. A process for the production ofmetallic calcium consisting in the fusion of anhydrous calcium salts, electrolyzing said salts, and maintaining the small cathode cool enough to prevent the depositing calcium from melting and tocause the deposition thereof in a spongy state.

2. A process for the production of metallic calcium consisting in the fusion of anhydrous calcium salts, electrolyzing said salts, maintaining the small cathode cool enough to prevent the depositing calcium from melting and to cause the deposition thereof in a spongy state, pressing the deposited calcium sponge formed while in the molten calcium salt and withdrawing it compressed.

In testimony whereof we have signed our names to the specification in the presence of two subscribing witnesses.

WILHELM BORCHERS. LORENZ STOCKEM.

Witnesses:

JOHN B. ADAMs, E. CURTZEN. 

